The current classification criteria include seven items: maximum eosinophil count >1 × 109/L, obstructive airway disease, nasal polyps, myeloperoxidase-ANCA (MPO-ANCA) or proteinase 3-ANCA (PR3-ANCA) positivity, extravascular eosinophil-predominant inflammation, mononeuritis multiplex/motor neuropathy not due to radiculopathy, and hematuria [2,3]. Here, PRTN3 is linked to mononeuritis multiplex.